The physiologic function of taurine is unknown with the exception of its particpation in the absorption and digestion of lipids mediated by the detergent effect of taurocholic acid. Of the many possible functions for taurine that have been suggested in recent years it appears that the most significant role(s) may be in cardiac physiology and/or in the transmission or modulation of nerve impulses in the central nervous system. It has been suggested that taurine may be able to regulate the excitability of the myocardium by possibly modifying the permeability of the membrane to potassium. Recently it was reported that the distribution of taurine in dog heart is not uniform. Whether these observations will help explain the findings that taurine stabilizes the electrophysiological processes in the myocardium is only speculative at this time. This proposal provides an approach to delineate the taurine-isethionic acid pathway in mammalian tissues by characterisation of the enzymes which are involved. In order to realize this goal, highly sensitive and specific assay systems will be designed. A rapid and extremely sensitive assay procedure for analyzing taurine levels in mammalian tissues based on an enzymatic derivative double isotope method will be designed and then a definitive study will be undertaken to measure rodent tissue levels of taurine and isethionic acid, thereby exploring the relationship between their concentration and anatomical location. Emphasis will be placed on the sulfonic acid levels in cardiac and nervous tissues since present data suggest a role for them in these tissues. BIBLIOGRAPHIC REFERENCES: J.B. Lombardini, "Regional and subcellular studies on taurine in the rat central nervous system", In Taurine (Eds. R. Huxtable and A. Barbeau) pgs. 311-326, Raven press, New York (1976). J.B. Lombardini, "An enzymatic derivative double isotope assay for measuring tissue levels of taurine", J. Pharmacol. Exp. Ther. 193, 301-308 (1975).